DT Catalogue

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T R A N S F O R M I N G Y O U R N E E D S I N T O S O L U T I O N S

PAUWELS INTERNATIONAL N.V.Antwerpsesteenweg 167 B-2800 Mechelen (Belgium)Tel. + 32 15 283 333Fax + 32 15 283 300

[email protected] ©

PA

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DT

03/0

3

Presentation of the Pauwels Group

Construction of a distribution transformer

the ferromagnetic core 6

the windings 10

the active part 12

the tank 14

finishing operations and testing 18

A comprehensive product range

Economic choice of transformers

Transformers and the environment

low-noise transformers 25

leakproof tanks and environmentally sound coolants 26

recyclable materials 26

radical exclusion of PCBs 27

electromagnetic compatibility 27

optimized use of raw materials 27

lower consumption of primary energy sources, due to the use

of transformers with low losses 27

Design, specifications and standards

Logistics

Quality assurance

Sales and customer service

After-sales service

Protection equipment

Contacts

34

CONTENTS

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6

20

24

22

28

29

30

32

33

34

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The Pauwels Group is one of the world’s leading transformer manufacturers.Group companies operate manufacturing plants and sales offices in three continents, with a worldwide network ofsales agents and customers in over 135countries.

5

From its base in Mechelen, Belgium, Pauwels International N.V.

acts as the overall holding company, defining the Group’s

corporate strategy and coordinating the marketing of its entire

product range.

The Pauwels Group is a full-line supplier, offering a wide

range of transformers consisting of:

liquid-filled distribution transformers

(15 kVA to 10,000 kVA/36 kV)

cast resin transformers (up to 10,000 kVA/36 kV)

power transformers (up to 575 MVA/500 kV)

auto-transformers (up to 400 MVA/500 kV)

HVDC station transformers (up to 315 MVA/500 kV DC)

The Pauwels Group’s six manufacturing plants are located in

Belgium (Mechelen and Gent)

Ireland (Cavan)

the United States of America (Washington, Missouri)

Canada (Winnipeg, Manitoba)

Indonesia (Bogor, Java)

In Saudi Arabia, distribution transformers and compact

substations are built under license from Pauwels.

Pauwels International N.V. and its subsidiary companies

employ a total of over 2,300 people, producing some

30,000 transformers each year with a total output of

more than 35,000 MVA. Pauwels International has a

consolidated annual turnover of some 350 million euros,

over half of which represents exports from Europe. More

than 500,000 Pauwels transformers have been produced

since the company’s formation in 1947.

Pauwels Trafo Service S.A. (Charleroi, Belgium) provides

transformer installation, repair and maintenance services.

PRESENTATIONof the Pauwels Group

Pauwels Contracting N.V. (Mechelen, Belgium) special-

izes in building conventional, mobile and modular

substations, and its core activities also include

transmission line projects.

Distribution transformers are manufactured in

Mechelen, Belgium (100 kVA to 10,000 kVA/36 kV)

Cavan, Ireland (15 kVA to 630 kVA/36 kV)

Washington, USA (45 kVA to 10,000 kVA/69 kV)

Winding area in Pauwels Trafo Ireland

This brochure provides information

about Pauwels’ liquid-filled distribution

transformers.

Our distribution transformers are usually

filled with mineral oil. As an alternative,

silicone liquid or synthetic organic esters

may be used as insulating medium and

coolant.

Main factory and headquarters of the Pauwels Group in Mechelen, Belgium (49,500 m2)

The reactive power dissipation can be lowered by limiting flux

disturbances and minimizing air gaps in the joints between the core legs

and the yokes. This is achieved by overlapping the core sheets while stack-

ing them (see page 9 under “Cutting and stacking of the core sheets”).

Material

The core is constructed using thin sheets of cold-rolled grain-oriented

magnetic silicon steel insulated on both sides. Conventional grain-

oriented steel (CGO steel) is used for transformers with normal

no-load loss characteristics, while transformers with reduced no-load

losses are built using higher-quality HiB steel (usually laser treated).

These steel sheets are 0.30 mm, 0.27 mm or 0.23 mm thick.

Extremely low no-load losses can be achieved only by using wound cores

made of amorphous metal. This has highly specific properties (very thin

sheets just 0.025 mm thick are used) and therefore it requires a specially

adapted design.

76

The heart of the matter: the ferromagnetic core

The cut of the core sheets and the material of the ferromagnetic core are

optimized according to the desired no-load characteristics and the

specified noise level. Extensive rationalization of the shape and the

clamping devices enables us to produce a core with minimum losses and

dimensions. This methodology optimizes the consumption of both

materials and energy, bringing benefits to the user, the environment and

the manufacturer.

The core has to be constructed in such a way as to limit the energy

losses caused by eddy currents and hysteresis to a minimum. This is

achieved by the use of silicon steel, a special soft steel with a 3.5% silicon

content, which is characterized by low hysteresis losses and high

resistivity. The core consists of a series of laminations made from very

thin sheets of steel insulated on both sides by an oxide layer (see opposite

under “Material”).

CONSTRUCTIONof a distribution transformer

The construction of a transformer comprises twoactive components: the ferromagnetic core and thewindings. Within the transformer industry, the coreand windings together are normally referred to as the“active part”. The passive part of a transformer is thecooling system, consisting of the tank andthe cooling liquid (mineral oil, silicone liquid or synthetic organic esters).

The ferromagnetic core Evolution of the quality of magnetic steel

9

Shape of core section

The vast majority of the distribution transformers built by Pauwels have an oval-shaped core

section, formed by combining the traditional stepped and fully filled round shape with a square

mid-section. This gives great flexibility in the height to which the steel sheets can be stacked,

thus allowing the ideal core section to be made for any design, while maintaining the use of

standard materials and dimensions. Using this method combines the benefits of a

rectangular core section (simplicity of production) with those of a round core section (excellent

short-circuit withstand capability of the windings).

Clamping devices

By using simple profiled-steel yoke clamping systems and a number of metal tensioning

bands, Pauwels has eliminated the need for either clamping bolts in the yokes (which would

distort the magnetic flux) or tie rods between the upper and lower yokes (which would require

the tank to be larger).

The core: main characteristics:

The 45° cut of the core

sheets guarantees optimum

flow of magnetic flux.

The oval shape allows

optimization of the core

section.

Low sound levels can be

achieved using the step-lap

stacking pattern.

The type of magnetic steel

is chosen according to

the desired loss level.

The simple supporting

structures and clamping

devices of the core contribute

to the compactness of

the design.

Cutting and stacking of the core sheets

Minimum magnetic flux distortion in the transition areas between yokes and core legs is

achieved by optimizing the cut of the core sheets and the stacking pattern.

First of all, the core sheets are cut at an angle of 45°, thus allowing maximum flow of

magnetic flux in the rolling direction. This is extremely important because losses in grain-

oriented magnetic steel are smallest in the direction of rolling. Then the sheets are stacked in

an overlap pattern of either single or multiple overlaps. The multiple overlap or step-lap method

offers additional benefits in terms of lower no-load losses and noise levels. Because they

involve a rather more complicated production technology, step-lap cores are preferably made

on fully automatic cutting and stacking machines.

Once the sheets are stacked, the core is compressed and glued to form a firmly-bonded

whole. This also helps to reduce noise levels.


The ferromagnetic core

Typical oval-shaped core cross section

Fully automatic cutting and stacking machine

High voltage windings

High voltage windings are almost exclusively of layered construction.

The copper or aluminium conductors are made of one or more round or

square wires, either with an insulating enamel coating or wrapped in

insulating paper. Each design is drawn up in accordance with the specific

characteristics of the conductor material to be used.

The insulation between the layers consists of pre-coated kraft paper,

applied either in sheet form or wound in a continuous narrow strip,

a technique which allows optimum adjustment of the insulation thickness

to the electrical gradient at each layer position.

The special diamond pattern of epoxy adhesive coated onto the kraft

paper cures during the drying process, bonding the windings into a single

structure.

The high voltage winding is wound directly onto the low voltage winding,

over the structures forming the main gap, giving maximum mechanical

strength, rigidity and compactness.

This mechanical strength is of the utmost importance since, in the event of

short-circuit, the windings have to sustain very high radial repellent forces.

The mechanical effect of these forces is minimal in round windings, since

these windings inherently have the ideal form to withstand radial stresses.

The mechanical effect is much greater in rectangular windings. In order to

combine the advantages of a rectangular core section (simplicity of

production) with the benefits of round windings (excellent short-circuit

withstand capability), Pauwels has developed the unique concept of

oval-shaped cores and windings (see drawing above).

10

Low voltage windings

Low voltage windings are usually made of copper or aluminium sheet

conductor (foil). The benefit of this is that any high voltage ampere-turn

asymmetry which might occur is compensated automatically by

an appropriate internal current distribution in the low voltage foil.

This reduces the axial stresses produced by short-circuits to a minimum

(down to 10% of those for conventional windings), thus enabling the axial

support construction to be greatly simplified.

The sheets and connectors welded onto them are made of electrolytically

pure copper or aluminium with a rigorously guaranteed conductivity.

Designs are adapted to the thermal, electrical and chemical characteristics

of each type of conductor, thus ensuring that both versions are of

equivalent quality, whether made of copper or aluminium.

The maximum voltage between each turn is only a few tens of volts. This

allows the insulation needed between the turns (foils) to be limited to 1 or

2 sheets of fine kraft paper only a few hundredths of a millimetre thick.

According to the design specification, this insulation may be coated with

a thermo-hardening epoxy adhesive which cures and bonds during

the drying process.

Foil windings may be wound either on a winding mandrel or, preferably,

directly onto the core leg. This ensures minimum play between core and

winding, for optimum rigidity.

The structures forming the “main gap”, i.e. the insulating space separating

the low and high voltage windings, are fitted directly onto the low voltage

foil winding, thus forming a part of it. These processes all enhance

the transformer’s short-circuit withstand capability.


Windings

The main benefits of layered windings are:

They form a simple winding,

which allows continuous or

semi-automatic winding.

The impulse voltage distribution

throughout the winding is

predictable and controlled.

Axial cooling ducts are simple

to build and fit.

Any taps required can be

brought out anywhere in the

winding through the layers.

Supplementary benefitsof foil windings are:

Greater simplicity in fitting

cooling ducts.

More even heat distribution

through the windings.

Semi-automatic winding

techniques can be used.

RECTANGULAR ROUND OVAL

RADIAL REPELLENT FORCES ACTING ON HV AND LV WINDINGS

CORE

HV LV

LOW HIGH

11

13

Bushings are mounted on the

cover, which is then fixed onto the

assembled active part. The next

step consists of connecting the

windings to the bushings.

The connection methods are durable and selected so as to ensure a solid, low-resistance connection between

the linked conducting materials, including junctions between aluminium and copper components.

Transformers are often fitted with an off-circuit tap changer. This switch allows the increase or decrease of

a certain number of turns while the transformer is disconnected from the circuit. Small variations in the nominal

supply voltage can be accomodated by adjusting the tap changer to keep the output voltage at the required value.

The off-circuit tap changer is always fitted on the high voltage side of the transformer, since this is where

the current is smallest. A second tap change switch is incorporated in transformers with dual high voltages in order

to change the high voltage. Tap changers and tap switches are controlled either by cable or by a drive shaft.

The voltage ratio of the active part is then tested, and the assembly is dried for a specified time in a forced-air

oven to remove the moisture from the insulating materials. This time depends on the quantity of insulating

materials, which in turn depends on the transformer’s rating and voltages.

Active part

Assembling cores andwindings to build anactive part

Assembly of cores and windings

to build an active part may be

carried out in either of the following

two ways:

If the windings have been wound

on a mandrel, the E-shaped cores

and the windings are transported

from their various construction

locations to the assembly area.

The windings are pushed over the

core legs and wedged up to fill the

spaces between the core and

winding as much as possible.

The magnetic circuit is then

completed by interleaving the

laminations of the upper yoke with

the laminations of the core legs.

If the windings have been wound

directly onto the core legs, the

three core legs are positioned on a

tilting table.

The upper and lower yokes are

then fitted highly accurately in the

same way as described above.


15

The reliability of hermetically sealed tanks is illustrated not merely by the tens of thousands of transformers

currently operating worldwide, but also by the stringent fatigue and overpressure tests carried out on

transformers of this type. Hermetically sealed tanks have been subjected to 11,000 expansion-contraction cycles,

which simulate the mechanical load on a tank over a service life of 30 years (at an average of 1 cycle per day).

The construction of these tanks is extremely simple. The bottom, top frame, corrugated fin wall panels and plain

wall panels are mounted on specially designed rotating welding tables and welded together. Small

production batch sizes resulting from the wide range of transformer designs produced do not yet allow this

process to be carried out by fully automated welding equipment. The skill and craftsmanship of highly experienced

welders and leak tests during production ensure leak-free finished tanks.

Cooling

Heat is generated inside a transformer by the effects

described by Joule’s law, hysteresis losses and

eddy currents (see chapter “Economic choice of

transformers”). This causes a rise in the temperature of

the windings and core. The temperature will reach

equilibrium when the quantity of heat generated per

second is equal to the quantity of heat removed

per second.

The operating temperature of liquid-filled transformers

is limited to around 100°C. While a higher operating

temperature can reduce the size, weight and cost of a

transformer for a given power rating, it shortens its

service life expectancy by accelerating the ageing of

the insulating materials. Cooling is optimized in

accordance with the maximum permissible

temperature and the total quantity of heat to be

dissipated, which depends on the transformer’s

loss level.

14

Construction

The vast majority of distribution transformer tanks are

constructed with cooling fins. There is only a very

limited demand for panel radiator types. As with

radiators, the purpose of cooling fins is to increase the

available contact surface for the cooling air. However,

in hermetically sealed designs the cooling fin design

also enables a degree of flexibility which is needed to

accommodate the expansion and contraction of the

liquid as it heats and cools, due to load and ambient

temperature. This allows the tank to be totally filled

(and hermetically sealed), with the clear benefit of

prolonging the transformer’s service life expectancy

and reducing maintenance.

In exceptional cases, e.g. small ratings and severe

dimensional limitations, the fins become so small that

they are no longer flexible enough, necessitating

The tank


the use of a gas cushion to allow the expansion of

the liquid. This gas cushion allows the internal pressure

to be maintained within the acceptable limits permitted

by tank flexibility. Occasionally, some customers

specify that a conservator must be fitted on top of

the transformer tank. This follows older rigid tank

design practice.

This cylindrical conservator acts as an expansion tank

for the cooling liquid when it expands as the windings

heat up. The conservator is often fitted with a gauge

glass, an air vent and an air dryer in an effort to ensure

that only dry air can come into contact with the

cooling liquid, and only at atmospheric pressure. If the

air dryer is not properly maintained, it can lose its

effectiveness and allow damp air to come in contact

with the cooling liquid.

Functions of the transformer tank:

It forms a container for the cooling liquid.

It acts as a heat exchange surface for the

dissipation of heat losses.

It is a protective, earthed safety shell.

It provides shielding against electromagnetic field

leakage caused by current-carrying conductors.

Hermetically sealed transformers offer indisputableadvantages compared with transformers fitted witha conservator, including:

The insulating liquid cannot come into contact with the air,

thus guaranteeing preservation of its dielectric integrity.

Reduced maintenance, e.g. no checking required of the air dryer,

no need to monitor the liquid for water ingress, etc.

They are cheaper to buy.

They occupy a smaller space, leaving more room for connections in

compact installations.

The protection equipment is often simpler than that fitted on

transformers with a conservator.

Corrugated fin wall panels

Standard tanks are equipped with:

securing lugs on the top frame of the tank to secure the transformer during transport

lifting lugs on the cover to lift the complete transformer and/or the active part

underbase welded to the bottom of the tank with bi-directional rollers (roller base)

filling hole on the cover (can also be used to mount an overpressure valve)

earthing terminals on tank cover and underbase or tank bottom

thermometer pocket welded to the tank cover and filled with cooling liquid

drain valve at the bottom of the tank (can also be used to take oil samples)

This standard package can be expanded to include other monitoring

and protection instruments (see chapter “Protection equipment”).

Surface treatment and painting

After welding, the tank is shot-blasted to remove

any surface impurities, leaving a clean prepared

surface for maximum adhesion of the paint coating.

Air-drying paint is then applied by spraying or flooding.

An alternative painting technique is electrostatic

powder coating, which is used for tank covers and

cable boxes and also for complete tanks in some

factories. Where powder coating is employed, further

chemical processes are needed before the powder

coating is applied.

Several coats of paint are applied, to a total thickness

of at least 100 microns, thus guaranteeing adequate

protection against corrosion for a transformer installed

indoors or outdoors. Tanks may be galvanized if

requested by the customer. This is often specified for

transformers which are constantly exposed to the

elements, as with pole-mounted or platform-mounted

transformers. Galvanizing is also recommended for

transformers used in polluted industrial areas.

The tank


17

1 4

2

7653

98

1011

212

4

State-of-the-art painting line

A state-of-the-art painting line, incorporating zinc phosphating, electrically

applied liquid paint and powder coating has been installed in the Irish

factory. This system is one of the most up-to-date developments in the

field of finishing and the quality obtained is comparable with that required

by today’s automotive industry for modern car bodies.

Tests by independent laboratories have shown that transformer tanks

treated in this way can easily withstand the 2,000 hours hot salt spray

scribed test carried out in accordance with the ASTM B117 and

DIN 50021 standards.

1 Lifting lugs2 Drain valve3 Thermometer pocket4 Earthing terminals5 LV neutral bushing6 LV bushings7 Filling hole

8 Off-circuit tap changer9 HV bushings10 Securing lugs11 Rating plate12 Underbase with rollers

(roller base)

Powder coating line

State-of-the-art painting line in the Irish factory

Finishing of powder-coated tanks

Flooding

1918

Mounting the active part in the tank

Once the active part has been dried in the forced air oven, it is given a final

comprehensive quality inspection and placed into the tank. The top cover

is then either bolted or welded onto the tank, as specified by the customer.

Both sealing methods are equally effective, although welding the cover

makes it easier to guarantee the seal is leakproof.

Filling

The transformers are placed in a vacuum chamber and filled with

pre-treated liquid (filtered, dried and degassed) under deep vacuum. This

ensures optimum impregnation of the insulation materials by the cooling

liquid, giving the insulation structure maximum dielectric strength.

Most transformers are filled with a high quality mineral oil which complies

fully with the requirements of IEC standard 60296.

In some cases, transformers are filled with silicone liquid (complying with

the requirements of IEC standard 60836) or synthetic organic esters

(complying with IEC 61099). The liquid acts both as a coolant and as an

insulating medium.

Finishing operations and testing


Testing

In the test bay, each transformer is subjected to a number of routine

measurements and tests.

Fitting of protection equipment

Once routine testing is completed, the protection instruments and other

accessories are fitted and the transformer is subjected to a final global

inspection. Subsequently, the rating plate (stating all the data required by

the norm or standard) is fixed to the tank with a bracket. The transformer

is now ready for packing and transportation.

Packing and transport

For transport by road, timbers are attached to the two U-shaped profiles

forming the roller base, thus enabling the transformer to be secured to

the load floor of the truck. A similar procedure is followed for container

transport. When specifically requested by the customer, and mainly

for transport by sea, the transformers are placed in strong wooden crates

or boxes.

Some customers specify the brand

and type of liquid to be used for

filling the transformer. Pauwels

carries stocks of several brands

and types of oil, which are then

piped from the storage tanks

through separate circuits to the

vacuum chamber. After a specified

stabilization period, the transformer

is taken to the test bay.

Routine measurementsand tests

Measurement of voltage ratios.

Vector group test.

Measurement of high voltage

and low voltage winding

resistances.

Dielectric test of high voltage

and low voltage winding(s)

(1 minute at rated withstand

voltage and nominal

frequency). This test is also

known as the “applied

overvoltage test” and is

intended to check the

insulation of one winding

from all other transformer

components.

Double voltage test (1 minute

at double voltage and double

frequency) induced via the

low voltage winding. This is

also known as the “induced

overvoltage test” and is

designed to check the

insulation within each

winding (turn to turn and

layer to layer).

Measurement of no-load

losses and no-load current.

Measurement of load losses

and impedance voltage with

the off-circuit tap changer in

the nominal position.

Measurement of the

resistances of the insulating

system between high voltage,

low voltage and tank

(Megger test).

In addition to standard transformer types for distribution applications, Pauwels also builds special

transformers for industrial applications. These non-standard types are the result of extensive product

development based on constant monitoring and evaluation of changing customer needs in the various

market segments. In some cases, special customer requirements have also led to the development of a

new product with its own characteristics. Our special distribution transformers have special mechanical

and/or electrical characteristics. In the majority of cases, these particular transformer types are designed

in such a way that they can be built using standard production techniques, thus requiring only a minimum

of modifications in the production process.

21

A comprehensive

mono and tri-mono transformers

transformers with special cable boxes

(filled with air or oil)

transformers with forced cooling

(by means of fans)

transformers with integrated protecting (fuses)

and disconnecting equipment (such as

the intrinsic safe transformer “TPC” for France)

SLIM® transformers (very compact high

temperature transformers)

Big DT (DT design concept up to 12 MVA)

Detailed information about our standard and special

distribution transformers is available upon request.

Special transformer types

The Pauwels product range includes the following special distribution transformers, although this list is

not exhaustive:

single-phase transformers (used mainly in the US,

Ireland and the UK)

dual voltage transformers

amorphous metal distribution transformers (AMDT)

steep-wave transformers

compact substations

three-winding transformers

auto-transformers

converter transformers

generator transformers

earthing transformers

substations with cable boxes and connectors for

Ring Main Units (RMUs)

phase shifters

PRODUCT RANGE

Total Owning Cost (T.O.C.) = purchase price + (P0*CP0) + (Pk*CPk)

T.O.C. = Total Owning Cost

P0 = guaranteed no-load losses (Watt)

Pk = guaranteed load losses (Watt)

CP0 = capitalization value for no-load losses stated by the customer (euro/Watt)

CPk = capitalization value for load losses stated by the customer (euro/Watt)

Evaluation of two distribution transformers, each with a nominal rating of 630 kVA but with different loss levels:

Tr. 1 630 kVA P0 = 870 Watt Pk = 5,750 Watt CP0 = 4.25 euro/Watt

Tr. 2 630 kVA P0 = 1,150 Watt Pk = 8,400 Watt CPk = 1.15 euro/Watt

P0 Pk price P0*CP0 Pk*CPk T.O.C.

Watt Watt euro euro euro euro

Tr. 1 870 5,750 7,550 3,698 6,613 17,861

Tr. 2 1,150 8,400 7,000 4,888 9,660 21,548

This table clearly illustrates that the lowest purchase price does not necessarily reflect the best economic alternative.

23

The Total Owning Cost (T.O.C.) of a transformer may be expressed by the following formula:

T.O.C. = purchase price + (P0*CP0) + (Pk*CPk)

Installation and maintenance costs may need to be added to this formula. Of course the transformer with

the lowest T.O.C. is the best economic choice in the long term. When a customer’s price inquiry gives

capitalization values, the optimum level of losses is calculated in the design department using specially developed

software. A further advantage of lower no-load losses is the fact that the level of noise generated is usually

significantly lower, due to the lower flux density.

Thus it is often economically justifiable to replace older transformers with high loss levels by the new generation

of low-loss transformers, since their lower losses ensure a significant return on investment after only a few years.

If the no-load energy losses are capitalized at a very high level, then amorphous metal core transformers

become an attractive alternative. The no-load losses of this type of transformer are some 75% lower than those

of an equivalent transformer with a conventional magnetic steel core.

22

1. No-load losses (P0), also called iron losses (PFe)

No-load losses occur in the core material due to hysteresis and eddy

currents, and are present almost continuously while the transformer is

connected to the electricity supply (i.e. 8,760 hours per year).

The hysteresis losses are proportional to the product of the frequency

and the amplitude of induction to the power of x, where x varies between

1.6 and 3.5 when induction is increasing: Ph ~ f.Bx.

Eddy current losses are proportional to the square of the product of

the frequency, the amplitude of induction and the thickness (d) of the mag-

netic steel: Pf ~ (f.B.d)2

2. Load losses (PK), also called copper losses (PCu)

Load losses occur in the windings, the connecting conductors and the

tank. They are caused by the effects of Joule’s law (Ohmic losses), eddy

currents and flux leakages. Ohmic losses are equal to the product of the

square of the current and the resistance of the conductor: Pj = R.I2

These losses are proportional to the square of the load, thus a load of 50%

of the rated load produces load losses equal to approximately 25% of the

rated full-load loss values.

Within certain limits, a manufacturer can increase or reduce no-load and/or

load losses by varying the current density, the induction level of the

magnetic steel, the choice of material for the conductors and the core, etc.

Lower losses always involve the use of a larger quantity of material and/or

higher-cost materials, thus raising the price of the transformer. However, its

energy consumption, and therefore running costs, will be lower. In order to

make an economically valid comparison of transformers with different loss

levels, a value reflecting the cost of the energy losses has to be introduced.

This value, expressed in monetary units per watt, allows financial

evaluation (or capitalization) of the losses and is therefore called

“capitalization value”. The capitalization values for no-load losses (CP0) are

considerably higher than those for load losses (CPk), which is logical

because no-load losses occur continuously.

Despite the fact that transformers are highly efficient electrical devices,inevitably some energy is lost during their long service life. This energy loss arises from the combination of no-load losses and load losses. These lossesconvert to heat which has to be removed during operation.

ECONOMIC CHOICEof transformers

25

Low-noise transformers

In many countries, there are strict

limits on the noise levels which

may be generated by trans-

formers in both urban and rural

locations. The primary source of

the noise produced is the

alternating magnetization of the

core steel, while the current-

carrying windings contribute only

a limited amount. Pauwels uses a

variety of techniques to limit noise

levels drastically, the most important being to reduce the induction in the

core, producing an appropriate core shape (e.g. the step-lap method), a

special clamping construction and the use of low-resonance tanks, etc.

This enables Pauwels to build transformers with extremely low noise

levels, down to within what we refer to as “whispering level”. Building

transformers with noise levels below 30 dBA (sound pressure at a distance

of 1 m) is an illustration of this. Pauwels has also carried out pioneering

work in the field of measurement of transformer-generated noise.

Engineers from our Research and Development department have refined

the noise intensity method (introduced by Brüel and Kjær in the early

eighties) and applied it to transformer noise measurement. This method

now has official recognition and is described in the IEC 60551 standard.

The noise intensity method allows more accurate measurement by

eliminating disturbances due to the near-field effect (*) and other nearby

sources, and also enables the noise generated by the transformer to be

measured when the ambient noise level is far in excess of the

transformer noise. This clearly makes the noise measurement and

evaluation process much simpler, while also allowing frequency analysis.

Besides frequency analyses, Pauwels laboratories can also carry out

vibration and resonance analyses.

Reference table dB(A)

20 rustling of leaves

30 whispering

40 library

60 normal conversation

70 traffic noise

100 heavy machine shop

120 rock concert

130 pain threshold

THE ENVIRONMENTTransformers and

A growing importance is attached tothe negative aspects of technology onpeople and the environment in modernsociety. The potentially disturbing orhazardous aspects of transformersinclude:

Noise pollution.

Land pollution, due to escaping oil caused by

leaks or explosions.

The use of PCBs (polychlorinated biphenyls) -

very toxic chemicals - in cooling liquids.

Electromagnetic fields: the effects of such fields

on human beings and instruments are not yet

fully understood.

Energy losses in transformers. Even though

transformers are generally highly efficient,

as explained earlier, some energy is lost in the

transforming process. This energy also has to

be generated somewhere and this generation

process has its own consequences, including

a rise in emissions of harmful combustion gases.

Visual pollution to the environment caused by

the siting of transformers and substations

without due consideration to the impact

on the landscape.

(*) Very close to a sound source, the air acts as a mass-spring system which stores the energy. The energy circulates without propagating and theregion in which it circulates is called the “near-field”. Only sound intensity measurements for sound power determination can be made here.

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✖Evolution of the weight of a 400 kVA transformer

Radical exclusion of PCBs

Pauwels operates a consistent, stringent PCB (polychlorinated biphenyl) monitoring policy: the test certificate

delivered with each Pauwels transformer certifies that its PCB content is less than 1 ppm (part per million).

Oil deliveries or transformers returned for overhaul or servicing are never accepted before an oil sample analysis

has provided conclusive proof that the liquid is PCB-free.

Pauwels’ customer service department acts as an intermediary for the collection and treatment of transformers

filled or contaminated with harmful PCBs by introducing the owner to officially accredited specialist waste disposal

companies.

Electromagnetic compatibility

All current-carrying conductors and machines create an electromagnetic field which can have an interfering effect

on sensitive (e.g. electronic) equipment. Therefore all products must be made with the highest possible

electromagnetic compatibility (EMC): they must not produce a disruptive field or be affected by other fields in their

vicinity. Pauwels liquid-filled transformers are ideal in this respect: their tank acts as a natural electromagnetic

screen, reducing the effect of external fields to negligible values.

Optimized use of raw materials

Extensive optimization has enabled Pauwels to succeed in building very compact transformers. Today’s 1,000 kVA

model is the size of the 630 kVA transformer of just a few years ago, for example. This optimization and

rationalization have simultaneously yielded significant savings in raw materials (copper, aluminium, magnetic steel,

metal, etc.) and coolants.

Lower consumption of primary energy sources, due to the use of transformers withlow losses

Pauwels also contributes to a cleaner and safer environment by offering low-loss transformers. Electricity utilities

using low-loss transformers will clearly need to generate less electricity to satisfy the same energy demand.

Generating less electricity involves lower consumption of primary energy sources (coal, gas and oil), thus

reducing emissions of the harmful combustion gases which cause phenomena such as acid rain and depletion of

the atmospheric ozone layer.

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Land pollution: the importance of leakproof tanks and environmentally sound coolants

An escape of coolant from the tank can cause land pollution and possibly

lead to the danger of fire when a spark or flame is present at the same

time. The “Wassergefährdungsklasse” or “WGK” (water pollution class) of

a liquid provides a measure of the threat posed by the liquid to

underground and surface water. This classification is based on the

biodegradability of the liquid. Most mineral oils and all silicone liquids are in

category 1, while esters are more biodegradable and classified as

category 0. A WGK of 0 is normally specified only when the transformer is

to be located in the vicinity of a water extraction area. Fire regulations and

fire insurance policy conditions often also lead to the choice of these

somewhat more expensive coolants. Their higher flash points and ignition

temperatures enable the transformer to be operated without excessively

stringent stipulations in respect of sprinkler installations or drip pans to

catch leakages, thus yielding significant reductions in installation costs.

The ingenuity of our designers, the craftsmanship of our welders,

the robustness of the materials we use and the multiple quality control

procedures carried out to check for leaks during the production process all

combine to ensure the long-term leak-free quality of our tanks.

Recyclable materials

One of the central themes of the Pauwels corporate policy is the quest to

reduce raw material consumption to a minimum. Waste materials from the

production process are collected and carefully sorted for sale as scrap for

recycling. A similar policy is followed by the specialist companies breaking

old transformers for scrap. Today’s Pauwels transformers are designed to

facilitate the highest possible degree of recycling. Over 90% of

the materials used can be recovered by simple procedures. Special

attention is paid to environmental impact even in the choice of the

smallest components, as illustrated clearly by the use of asbestos-free

gaskets, for example.

C

Transformer filled with synthetic organic esters in accordance with theIEC 61099 standard

THE ENVIRONMENTTransformers and

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Quality logistics management produces fast delivery times, punctual and complete delivery, and correct and rapid

handling of administrative procedures. Careful construction of the Group’s computer network and information

systems has built a superbly efficient information flow system connecting all the various departments of the

Pauwels organization. The group operates a Just-In-Time material flow system, optimized using specialized

computer software, automated warehousing systems and firm contracts with accredited suppliers.

Pauwels supplies transformers to customers in over 135 countries around the world. This requires the assistance

of specialist transporters with wide experience in multi-mode transportation. In addition to the complexities

specific to long-distance destinations, complicated logistical problems can arise when transformers have to be

installed in locations where access is difficult.

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DESIGNspecifications and standards

Pauwels transformers are designed to meet all the most recent national

and international standards such as IEC, ANSI/IEEE, CEN/CENELEC, BS,

DIN/VDE, NEMA and CSA, etc. Within the distribution transformers

product group, the product development department is responsible for

managing and updating the internal standards database. Engineers from

this department play an active role in a wide range of engineering

standards committees and international working groups, where they are

able to keep up-to-date with the latest developments in technical

standards.

Pauwels has designed standard transformer models for a large number of

markets, each fully meeting or even exceeding the national standards and

requirements of each market. Other transformers are standardized to the

specifications of individual major customers such as electricity utilities,

large contractors and heavy industrial companies. All other transformers

are designed individually to meet the customer’s specific requirements.

This approach has enabled Pauwels to achieve extensive automation

in the design and construction areas, leading directly to an ability to

offer attractive prices and fast delivery. The high degree of customer

satisfaction and the numerous accreditations achieved after stringent

approval procedures illustrate the success of the Pauwels product

development strategy.

LOGISTICSThe complex chain of processes,

from initial offer through to final

delivery, is managed by the logistics

department. In view of the strongly

international character of the

Pauwels Group’s business, this

requires flawless organization and

extensive experience.

stock controlpurchasing

planningfactory

distributionof drawings

customer infoorder status

test bayfinal control

production

delivery of materials

drawings & planning

reservations

design drawings

QUALITY ASSURANCEcertified to ISO 9001 and based on self-assessment

The high reputation ofPauwels transformers isa product of the comprehensive attentionto quality.

Operating a certified quality system to ISO 9001 standards is merely a

precondition for achieving consistent quality. Within the Pauwels

organization, quality control is carried out at each design and production

phase through a self-assessment system.

Each workstation has a description of the tasks to be carried out and

the accompanying quality control procedures. A component is passed on

to the next workstation only after the worker concerned has carried out

the specified quality control procedures and approved the component. Any

material or component failing a quality test is rejected immediately.

Thus each worker checks his (her) own production and regards the next

workstation as his (her) customer. The quality department monitors all

quality control documents and carries out additional inspections at

strategic points in the production process. This allows immediate action to

be taken and any modifications to be made as required.

Materials purchased from approved suppliers are subject to goods inwards

checking which can vary from simple identification to comprehensive

testing in the physical chemistry laboratory. All raw material and

component suppliers must meet ISO standards.

Each transformer is subjected to the full range of specified tests before

release to the customer. Testing to IEC or ANSI specifications includes all

routine tests and measurements and may be complemented by type

and/or special tests. These supplementary tests are carried out either on

the customer’s request or as part of an internal sampling procedure to

ensure continuous quality monitoring.

All testing is performed within the company with the exception of dynamic

short-circuit tests, which are contracted out to accredited external

laboratories such as KEMA, LABORELEC, EDF, CESI, FGH and other

independent testing institutions. Many customers have carried out quality

audits and inspections in the various Pauwels facilities and repeat them

regularly to assure themselves of a consistently high quality level.

In addition to the national and international standards, e.g. IEC, ISO, etc.,

some customers also use their own measuring and testing schemes

which often involve tests in independent laboratories.

Commitment to quality runs throughout the company: Research andDevelopment, Design, Production, Quality Control, Logistics andAdministrative Services. The Human Resources department maintainsan ongoing programme of quality consciousness and quality enhancement training for all the company’s employees.

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Sales

The Pauwels Group sales organization is structured to ensure the shortest

possible lines of communication between customers and Group companies.

This goal is achieved by working through a network of small, efficient sales

offices and specialist representatives with an expert knowledge of local

conditions and of the customer’s requirements.

Sales offices operate in France, Italy, the USA, Colombia, Indonesia,

Saudi Arabia, the United Arab Emirates, Nigeria and Zimbabwe.

Customer service

Inquiries and orders are handled by multidisciplinary customer service teams, where technical, commercial and

administrative skills are blended exactly as needed to deliver what each different customer type demands:

the right product at the right time at the right price.

Each customer service team is therefore specialized in processing inquiries and orders with very specific

characteristics in terms of customer requirements and/or transformer types. This results in a high degree of

overall customer responsiveness illustrated by timely return of fully detailed quotations, high delivery reliability

with orders and fast information exchange throughout the contract period ensuring well informed customers.

The customer service teams work closely together with the Logistics Department (Purchasing, Planning,

Transport and Invoicing) and the After-Sales Department in order to guarantee the highest possible levels of

customer satisfaction.

SALES ANDCUSTOMER SERVICE

Production facilities

Subsidiary companies

Regional offices

Agents & sales contacts

The Pauwels organization offers an extensive range of support services to

customers after delivery of their transformers, including:

a 24-hour helpline, with teams on permanent

standby to carry out all possible urgent

repairs, etc.

maintenance and repairs to transformers either

on-site or in our well-equipped workshops

oil sampling - to assess the insulating

condition of the liquid

- to analyze dissolved gases

- to determine PCB content

drying, degassing and filtration of the coolant

oil cleansing to remove PCBs

supply of spare parts

provision of replacement transformers

modifications such as:

- connections (e.g. bottom entry

or top entry cables)

- replacement or conversion of

accessories such as Buchholz

relays, liquid level indicator

gauges, pressure relays, etc.

overhaul and replacement of the off-circuit

tap changer

increasing transformer power capacity by

converting to forced cooling

(installation of fans, etc.)

training for customers’ maintenance staff

advice to customers on how to operate and

maintain their transformers

AFTER-SALESservice

Documents

DT Catalogue